Integrated circuits are often packaged prior to sale and use, by physically and electrically connecting them to a package substrate, and then covering them in some manner against the package substrate. The package substrate provides all the necessary electrical connections between the electrical contacts for the integrated circuit, on one side of the package substrate, and the electrical contacts on either the printed circuit board or socket, that will connect to the other side of the package substrate.
As the term is used herein, “integrated circuit” includes devices such as those formed on monolithic semiconducting substrates, such as those formed of group IV materials like silicon or germanium, or group III-V compounds like gallium arsenide, or mixtures of such materials. The term includes all types of devices formed, such as memory and logic, and all designs of such devices, such as MOS and bipolar. The term also comprehends applications such as flat panel displays, solar cells, and charge coupled devices.
As the design of a given integrated circuit evolves, it tends to be reduced in the size of the die on which it is formed. In addition, families of integrated circuits that provide the same basic functionality, but with different options or implementations, may also vary in size. Typically, a different package substrate is designed for use with each one of the different sized devices.
Traditionally, the locations of the electrical connections on both sides of the package substrate are determined based on general routing rules. The electrical connections on the die side of the package substrate are often placed according to the location of the contacts on the die, depending on the type of integrated circuit used. The electrical connections on the board side of the package substrate are often placed according to the easiest method of routing out the connections, allowing for proper signal isolation and other similar considerations. Also, the size of the package substrate that is used for a given die typically varies with the size of the die, with bigger substrates for bigger dice, and smaller substrates for smaller dice. All of this tends to change the pin out locations for each of the different package substrates.
The result of this design and fabrication process is that the package substrates for the dice within a given family of integrated circuits will all tend to have different sizes and different pin outs, just like the different integrated circuits that are mounted to them. Unfortunately, this requires either a different connection pattern or socket on the circuit board that is designed to use the packaged integrated circuit, for each of the different sizes or varieties of integrated circuit that might be used on the circuit board. This adds to the number of different circuit boards that must be produced and inventoried, adds to the complexity of board assembly, and thereby tends to increase costs. This also limits the ability to migrate to a different integrated circuit size during the product definition and development phase.
What is needed, therefore, is a system that overcomes problems such as those described above, at least in part.